E. I. du Pont de Nemours (DuPont) has been manufacturing Tyvek.RTM. spunbonded olefin sheet products for a number of years. During this time, DuPont has developed two basic styles of flash-spun nonwoven sheet products: area bonded material and point bonded material. Area bonded material is thermally bonded generally uniformly across the area of the sheet. Point or pattern bonded material is thermally bonded at points or in a pattern where the pattern creates portions which are more strongly bonded and not as strongly bonded. As such, area bonded products are typically stiffer than point bonded and have a paper-like feel. Point bonded flash-spun nonwoven products tend to have softer fabric-like feel. Point bonded flash-spun material is most commonly used in protective apparel. Area bonded products are used in envelopes, medical packaging and air infiltration barriers in construction applications.
Focusing on protective apparel, the comfort of the wearer is a factor that takes into consideration a lot of properties of the sheet material. DuPont has done much development work to increase breathability and strength of the flash-spun nonwoven materials. One consideration that is commonly recognized but difficult to measure is softness or hand. Softness is one of the key fabric properties influencing comfort. Improved softness for flash-spun nonwoven fabrics without diminishing other properties would be recognized as an upgrade or improvement that would be appreciated by customers or users. Another interesting property for apparel is its quietness or noisiness. Garments, such as protective apparel, made of fabrics which make noise as the wearer moves are perceived as uncomfortable.
It is believed that added softness would also be favorably received for area bonded materials. In particular, area bonded flash-spun nonwoven materials tend to be somewhat noisy when flexed. In some construction applications, the air barrier may not be fully restricted from movement when exposed to pressure changes such as from a door opening or closing. The audible rippling of the air infiltration barrier would not be desirable. Thus, again, a softer product may reduce or eliminate the noise associated with a paper like sheet material.